Modified phenol-furfural molding compositions and process of making same



Patented Aug. 12, 1952 UNITED srnrss accuser MODIFIED PHENOL-FURFURAL I MOLDING COMPOSITIQNS AND PROCESS OF 'MAK- ENG SAME Stephen Frederick Pearce, Upper Tooting, London, England, assignor to Imperial Chemical 1 Industries Limited, Britain corporation of Great No Drawing. Application April 5, 1949, Serial No.

85,717. In Great Britain dpril 21, 194.8;

This invention relates to the production of improved thermosetting moulding compositions and, more particularly, to the production of improved thermosetting phenol-furfural moulding compositions.

By the expression thermosetting phenolfurfural moulding compositions as used hereinafter throughout the specification we mean filled or unfiled resin compositions, in a state of subdivision suitabe for feeding into moulds used in the art, in which the resin components are a permanently fusible, soluble phenol-furfural condensation product and a methylene donating hardening agent.

By methylene donating hardening agents we meansubstances such as hexamethylene tetramine, which provide the additional methylene groups required to convert the fusible, soluble resin to the infusible, insoluble state.

Suitable phenols for the production of fusible, soluble phenol-furfural resins include phenol, m-cresol, resorcinol, 3:5-xylenol andcommercially available mixtures of these and their isomers.

Thermosetting moulding compositions are produced by blending together the resin and the hardening agent and, if desired, one or more fillers, a mould lubricant, which may be, for example, zinc stearate, any other desiredingreclients such as basic materials, for example, lime or magnesia, plasticisers and dyes and/or pigments, and thereafter malaxating the blend, for example, in a Banbury mixer and/or on heated rolls until the composition has the desired flow and the constituents of the blend are well mixed together. The compositions are then converted to a form suitable for loading into moulds or compacting in pelleting machines. Suitable nilers for such compositions include woodflour, paper, cotton in various forms, mica, asbestos and other inert materials. If compositions suitable for the production of high impact strength mouldings are desired, fillers in the form of string or diced fabric may be used. The compositions may then be prepared by mixing the resin, which may be in the form of a spirit solution or aqueous suspension, and hardening agent with the fillers and other ingredients in a suitable mixer such as an edge runner mill or a Baker-Perkins mixer until the fillers are well impregnated with the resin and thereafter drying, heating being continned until the compositions have the required flow.

Mouldings prepared from phencl-furfural moulding compositions, especially those containing resins made from commercially available mix- Claims. (or. zen-54) tures of cresols and xylenols, often suffer from the disadvantages of being slow to cure andbeing diificult to remove from hot moulds because they tend to be soft'at the temperature of-the mould.

' This softness may lead to deformation and dam age to the moulding during removal from the mould. The mouldings may also stick to the mould and may even require the use of considerable force in their extraction therefrom. These difficulties, as will be readily appreciated by those skilled in the art, cause a decreased speed of productionv and increased cost of articles moulded from such compositions. H

In the copending United States application Serial, No. 13,943 filed March 9, 1948 it is disclosed that the above disadvantages which also occur in phenol-formaldehyde moulding compositions, can be overcome therein by the moor--v poration of a boric acid. We have now found that these disadvantages in phenol-furfural moulding compositions can also be overcome by the incorporation of a boric acid therein at any stage during its manufacture.

An object of the present invention is to provide a process for the production of improved phenol-furfural'moulding powders. Another object is to provide a process for the production of phenol-furfural moulding compositions having increased rates of cure. A further object is to provide a process for the production of phenolfurfural moulding compositions having increased plasticity when subjected to moulding conditions. A still further object is to provide a process for the production of phenol-furfural moulding compositions which give mouldings having increased hot strength and improved electrical properties. Other objects will appear hereinafter.

According to the present invention these objects are accomplished by a process comprising incorporating a boric acid into a phenol-furfural moulding composition, as hereinbefore defined, at

any stage-during its production.

The boric acid is used in amount from 0.1 to 20 per cent and preferably from l'to 12 per cent by weight of the resin plus methylene donating hardening agent and may be added to the other ingredients in any desired manner, for example, it may be added either in a dry state or in solution .to the fusible, soluble resinor to any-of the other ingredients. Alternatively, it may be added to the blended material before or during malaxation. It is preferred, however, to add the bone acid at an initial blending stage of the resin with the other ingredients as this method: is most convenient for plant operation. Boric acid in a 'ing a radius-of curvature of contact of the plunger This water, the bulk of whichislostduringworb ing, may be used in amount from2 tofi percent by weight of the composition.

A valuable feature of the present invention is that it allows the use of cresol...and/or xylenol mixtures which are low in content-of themeta...

isomers for the production of satisfactory moulding compositions. The use of such low grade materials has not hithertd'been possible as resins produced therefromdiave'not been sumcientlyreactive.

Our invention is further illustrated by the following example; in which all parts are by weight, but-it isito be. understood that our invention is in fie-way limited by. this. example.

Preparation of resin Dry'phenol and furfu'ral were condensed-in. a molecular ratio of 1.0 to 0.83 by heating. in the presence 'of 0.3 gm. of potassium carbonateper gramemoleculeof--phenol.- The mixture was. heated slowly -under Y conditions which, while .re taming the furfural, allowed the water to distil off"'slowl'y as formed. The temperature was. raised to 200-205 0. anddistillati'on continued untit-the requisite amount of water had been re.-' moved. The resinwas then cooled and disintegrated" and had a melting poi-nt of 65 C.

Preparation of moulding. compositions Two. mouldingcompositions were made by compoundingatogether. on hot rollsithe ingredients showninthenfollowingtable, which also shows the. moulding. ,properties of the compositions; Thepropertiesgiven are (a) a cup flow (as deter-- minedby themethod-of B. 'S.S..771), Ib) cup curerf-minimumfltime to produce a blister-free moulding ,in.the;,Bs S; S5771 cup flow test; the time-beingmeasured from the moment the mould is completely. closed-.to the moment when the mould-deepened). and. '(c) the: ease of deformation of the hot. moulding immediately on remoyalfromthemould. Note: The ease of deformation is. an arbitrary measure of the hot strength of the moulding and is determined by therfollowing method. The hot cup is taken straight from the mould and .placed immediately on its side in anapparatus containing a suitably shaped depression suchthat the cup lies with its axispf symmetryina horizontal plane. A loaded plungenltotal load 10.5 lbs.) is' then lowered on to. the upper surface of the cup'near the open end. theplurigerbeing constructed of a semicircularpieceof 1%; thick mild steel plate, havin. The point of is .in. from the open end-of the cupand vertically above the central axis. Under this. deforming load, the sides of thecup are. partially squeezed together. The decrease in diameter of the open end, calculated as a percentage of the original diameter, is termed the ease of deformation.

TABLE Parts Phenol'furiural resin 42. 0 42. Woodfiour 53. 5 53. g 3. 0 3. 0 0.5 0. 5 1.0 l. 0 3.0 4. 0

T'ofiil. 104. 0 107. 0

Cup flow (secs.). 14 14 Cup cure at 163 O..(seos-.) 85 67. 5 Ease of deformation (after secs. cure) 25 12. 5

1. A process as set forth in claim 9 wherein the boric acid is used in anamount from 0.1 to 20% by weight of the fusible soluble resin plus the hexamethylene tetramine.

2. A process as set forth in claim 9 wherein-theboric acid is used in an amount from 1 to 12% by weight of the fusible soluble resin plus hexamethylene tetramine.

3. A process as set forth in claim 9 wherein the boric' acid is incorporated during the initial blending of the fusible soluble resin with the hexamethylene tetramine.

4. A process as set forth in claim 9 wherein a small amount of water is incorporated during the working of the composition.

5. A process as set forth in claim- 9 wherein water in an amount of from 2 to 6% by weight of the composition is incorporated.

6. A newand improved two-stage phenolfurfural molding composition as set forth in claim 10 wherein said boric acid is present in an amount .of fromdl to 20% by weight of the fusible soluble resin plus hexame'thylene tetramine.

'7. A new and improved two-stage phenolfurfural molding composition as set forth in claim 10 wherein said boric acid ispresent in an amount from 1 to 12% by weight of the fusible soluble resin plus hexamethylene tetramine.

8. A new and improved. two-stage .phen'ole furfural molding composition as set forth in claim 10 wherein said boric acid is present in an amount of from 0.1 to 20% by weight of the fusible soluble resin plus the hexamethylene tetramine and wherein water. is present in an amount of from 2 to 6% by weight of the molding com-- position..

9..A. process for the production of a new and improved two-stage phenol-furfural molding composition in which the two-stage resin consists' of 'a fusible, soluble phenol-furfural resin and hexamethylene tetramine which comprises intimately admixing boric acid with these ingredients.

10. A new and improved. two-stage phenolfurfural. molding composition comprising an intimate mixture of a fusible, soluble phenolfurfural resin, hexamethylene tetramine' and boricacid.

STEPHEN FREDERICK PEARCE.

Number 2.368.893

Name Date Monier Nov. 28. 1944 

10. A NEW AND IMPROVED TWO-STAGE PHENOLFURFURAL MOLDING COMPOSITION COMPRISING AN IN TIMATE MIXTURE OF A FUSIBLE, SOLUBLE PHENOL-/ FURFURAL RESIN, HEXAMETHYLENE TETRAMINE AND BORIC ACID. 